Database indexes are data structures used to retrieve data stored in database tables. Through the use of indexes, desired data can be located without scanning through every row in a database table each time the table is accessed. Building an index on a table having sorted data rows on the index key column values involves reading the data rows, extracting the index key column values, and building the index rows. Indexes are conventionally generated using a serial query plan which means that a single process does all of the processing to construct the index.